1. Field of the Invention
The present invention relates to a mobile communication apparatus capable of recording or reproduction.
2. Description of the Related Arts
FIG. 19 is a block diagram showing a conventional mobile communication apparatus using digital speech signals for communication, for example, a digital portable telephone. In FIG. 1, reference numeral 1 denotes a microphone which supplies speech into the mobile communication apparatus; 2 denotes an A/D converter for converting analog speech signals into digital speech signals: 3 a loudspeaker for performing speech output for the mobile communication apparatus; 4 a D/A converter for converting digital speech signals into analog speech signals; and 5 denotes a digital speech signal processing section for compressing the digital speech signals derived from the A/D converter 2 and for expanding the received compressed digital speech data, which can be, for example, a speech codec. Reference numeral 6 designates a time division multiplex timing control section for timing adjustment which is time division multiplex accessed. Reference numeral 7 signifies a control section for controlling the digital speech signal processing section 5 and the time division multiplex access timing control section 6.
The action thereof will be described hereinbelow. In the diagram, when transmitting a speech data, analog speech signals which have been input in the form of speech through the microphone 1 are converted into digital speech signals by the A/D converter 2. The thus obtained digital signals are supplied into the digital speech signal processing section 5 for signal processing. In the digital speech signal processing section 5, the digital speech signals are compressed to have a lower bit rate. The compressed digital speech data are then output with error correction codes attached thereto. By way of example, the North American digital mobile phone employs as the digital speech signal processing section 5 a speech codec which compresses the digital speech signals to a coding rate in the order of 8 kbps (actually a coding rate is 7.95 kbps and total coding rate is 13 kbps when an error correcting code is added). In the time division multiplex access timing control section 6, the digital speech signals compressed in the digital speech signal processing section under the control of the control section 7 are subjected to the adjustment of timing and supplied with control signals for the formation of multiplexing signals. The multiplexing signals are radio transmitted to a base station. From the base station, speech data is transmitted to the other party in communication by way of a communication network such as a public telephone network.
When receiving the speech data, it is transmitted from the other party in communication through the communication network to the base station which performs processing such as signal compression to form speech signal data (multiplexing signals). In the time division multiplex access timing control section 6, compressed digital speech data are taken out of control signals involved in the multiplexing signals, and then input into the digital speech signal processing section 5. In the digital speech signal processing section 5, signal error correction processing is carried out based on the error correction codes imparted to the compressed digital speech data, and the compressed digital speech data are expanded. In the D/A converter 4, the digital speech signals derived from the digital speech signal processing section 5 are converted into analog speech signals, and output as speech through the loudspeaker 3.
In the case where a recording/reproducing function is loaded into the thus configured portable telephone or the like, for example, where the speech of the other party is recorded and reproduced, the conventional configuration is as shown in FIG. 20. In the diagram, reference numeral 8 denotes a recording/reproducing section for recording speech signals and for reproducing the thus recorded speech signals, which may be comprised of a recording element such as a RAM. Reference numeral 9 denotes a switching section to be connected with the recording/reproducing section 8.
The action thereof will now be described. The received speech data are subjected to expansion processing in the speech signal processing section 5. When performing ordinary communication, SW1 and SW2 of the switching section 90 are both off so that the digital speech signals are output intact to the loudspeaker by way of the D/A converter 4. When recording the voice of the other party during the communication, the control section 7 issues a control signal to the switching section 9. As a result, the SW1 of the switching section 9 is turned on to allow the digital speech signals from the speech signal processing section 5 to be output to the D/A converter 4 and to the recording/reproducing section 8. Afterwards, the recording/reproducing section 9 receives a control signal for starting recording from the control section 7, to initiate the recording of the digital speech signals derived from the digital speech signal processing section 5. When terminating the recording, the control section 7 issues a control signal for ending the recording to the recording/reproducing section 8 to stop the recording and turn the SW1 of the switching section 9 to OFF.
In the case of reproducing the recorded speech signals, the control section 7 issues a control signal to the switching section 9 to turn the SW2 of the switching section 9 to ON. Afterwards, the recording/reproducing section control signal for initiating the reproduction from the control section 7 to output the recorded digital speech signals to the switching section 9. With the SW2 being ON, the digital speech signals supplied into the switching section 9 are converted into analog speech signals by the D/A converter 4 and are output through the loudspeaker 3 in the form of a voice. After the completion of the output of the recorded speech signals, the control section 7 issues a control signal for ending reproducing to the switching section to turn the SW2 of the switching section 9 to OFF to complete the reproduction.
In the case of loading a recording/reproducing function into the mobile communication apparatus such as the conventional portable telephone, if the amount of signals being recorded exceeds the capacity of the recording memory in the recording/reproducing section 8, originally recorded speech signals must be deleted and replaced with new speech signals for recording. The increase of the memory amount in the recording/reproducing section 8 may lead to an increase of the capacity, which may impair the portability of the portable telephone.